Process of making cigarette filters, and apparatus therefor

ABSTRACT

In a process of making multiple filters for cigarettes, a succession of uniformly spaced filter wads are secured to a continuously fed cover strip; this assembly is moved past (and in contact with) a filler head having a filling aperture while a suction device - disposed ahead of the filling aperture and above the wads - produces a partial vacuum within a space (between two adjacent wads) whereby filter material moves from the filling head into the evacuated space. The edges of the cover strip then are brought together and overlapped and finally are fixedly secured to each other.

United States Patent 1 1 Burrus et al.

Oct. 2, 1973 12 v p sw PROCESS OF MAKING CIGARETTE FILTERS, AND APPARATUS THEREFOR [76] Inventors: Charles Burrus, En Chatillon,

Boncourt; Serge Boegli, Eggbuehlstrasse 8, Zurich, both of Switzerland [22] Filed: Oct. 1, 1971 Foreign Application Priority Data 3,312,151 4/1967 Molins 93/! C Primary Examiner-Andrew R. .luhasz Assistant Examiner-James F. Coan Attorney-Pierce, Scheffler & Parker [57] ABSTRACT In a process of making multiple filters for cigarettes, a succession of uniformly spaced filter wads are secured to a continuously fed cover strip; this assembly is moved past (and in contact with) a filler head having a filling aperture while a suction device disposed ahead of the filling aperture and above the wads produces a partial vacuum within a space (between two adjacent wads) whereby filter material moves from the filling head into the evacuated space. The edges of the cover strip then are brought together and overlapped and finally are fixedly secured to each other.

24 Claims, 9 Drawhi g Figures 1 l E km 20 a0 31 PATENTED 2 sum 3 [1F 5 H v v \\\p & m 2 n ma j Q 3 3 n .VN Q". GP 4 M mm w J2 m 2 9 P in: 3 m T L 6 7 1 mm we 3 PATENTEUUBT 2 m 3.762.281

, SHEET BF 5 Fig.7

PATENTED SHEET 5 [IF 5 PROCESS MAKING CIGARETTE FILTERS, AND APPARATUS THEREFOR The present invention relates to a method of manufacturing a cigarette filter, in which sections of fibrous and of free-running filter materials are arranged in succession, and to a device for putting that method into practice.

In one known method of making multiple filters, individual filter sections are attached, spaced apart, to a cover strip, which is wrapped partly round them, and then a free-running filtering medium is discharged from a hopper into the spaces between the filter sections. By regulation of the depth of the filter material in the hopper, it is sought to regulate the pressure of that material in the base of the hopper and hence the degree to which the said spaces are filled. The drawback of this method is that the degree of filling can scarcely be controlled by the depth of filter material in the hopper and is unsatifactory even at low speeds of production.

In another known method for the production of multiple filters, the individual filter chambers are charged with the free-running filtration material with the aid of a wheel containing recesses round its periphery or by means of a chaincarrying cups. This mechanism is very complicated and again does not enable the degree of filling to be matched to the nature of the filtering medium used.

In yet another known device, the individual spaced filter sections are wrapped round, up to an upward facing opening, with an initial cover strip, the width of which is less than the circumference of the filter sec- 'tions to be covered, this strip containing perforations for the passage of air. The resultant assembly is fed to a filler head, where, to accelerate filling, air is drawn from below, through the initial cover strip, from the filter spaces to be filled with the free-running material. Upon completion of filling, the whole requires further wrapping in a second, wider, cover strip. This method, too, is very complicated and it is not possible for the units being filled to be supported on a conveyor belt below the filler head, which results in further disadvantages. Moreover, the use of two cover strips increases production costs and leads to the formation of false air passages in the finished filter.

The purpose'of the invention is to provide a method and a device free from the above drawbacks, with which it is a simple matter to fill the filter spaces faultlessly, the filling being regulated according to the nature of the free-running filtering medium used.

The method here proposed is characterised by the fact that a succession of filter elements or wads, uniwads and the free-running filter material, after which the overlapping edges of the strip are firmly cemented together.

It is preferable to use a cover strip coated with a thermoplastics on the side cominginto contact with the filter wads and to join these to the cover strip by the use of a heater to soften the thermoplastic coating at least at particular points.

The invention also has as its object a device for putting the proposed method into practice, characterised by the incorporation of the following components: a feed mechanism for continuously feeding a succession of uniformly spaced and axially aligned filter wads on to a continuously fed cover strip; means of fixing the individual filter wads to cover strip; means of guidance and conveyance, by which the cover strip bearing the filter wads is guided and continuously fed forward; a forming member in the vicinity of the said means of guidance and conveyance, by which the cover strip, as it moves forward, is wrapped round the filter wads attached to it so as to form at least approxmately a letter U; a suction arrangement fitted above the means of guidance and conveyance, such that it makes contact, between the arms of the U-shaped cover strip, with the upper sides of the filter wads travelling forward with the cover strip and the facing inner surfaces of the U- shaped cover strip; a filling head for charging freerunning filter material ,into the spaces between the wads, this filling head being situated above the means of guidance and conveyance and connected to the suction arrangement by a common sliding surface which makes a sealing contact on the upper sides of the filter wads travelling forward with the cover strip; a guide which converts the cover strip into a tube completely enclosing the filter wads and the spaces between them filled with free-running filter material, so that the edges of the cover strip overlap; means by which the overlapping edges of the cover strip are joined together; and means whereby the tube filled with sections made up of filter wads and free-running filter material is divided up into given lengths.

It is desirable for the suction arrangement and the filling head to be connected by a common elongated sliding member extending in the direction of travel of the filter wads and providing a sliding face which forms a sealing contact on the upper sides of the wads travelling forward with the cover strip, for the width of the sliding member to be at least approximately equal to the diameter of the wads to be wrapped in the cover strip, and for the side faces of the sliding member to be formly spaced and in axial alignment, are secured to a continuously fed filter-tip cover strip; then the filter wads and the cover strip for forming spaces with a feed aperture between the wads are moved past, and in contact with, a filler head having at least one filling aperture, while a suction device situated (in relationto the direction of travel of the filter wads)-before the filling aperture and above the wads produces, through the feed aperture of the spaces and through'the filter wads moving towards the filling aperture, a partial vacuum within the spaces to be filled, so that a given quantity of free-running filter material passes from the filling head into the spaces between the wads, the edges of the cover strip then being brought together and overlapped so as to form a tube completely enclosing the filter parallel to each other and to the direction of travel of tact with the facing surfaces of the arms of the U- shaped cover strip.

It is also desirable for the lower part of the storage container to be cylindrical, for its means of closure to consist of a scoop-shaped closing member bearing against the inner face of this cylindrical part and rotating about the longitudinal centre line thereof, and for the closing edge of the closing member to run helically about the longitudinal centre line of the cylindrical part of the storage container, so that as the closing member is turned in the direction for opening, it is initially that end of the discharge slot that lies towards the suction aperture which is freed, this being followed by those parts of the discharge slot which are farther from the suction aperture as the closing member continues to turn.

The invention is described hereunder, by way of example, in conjunction with the accompanying drawings, in which:

FIG. 1 is a diagrammatic side elevation of a device for producing a cigarette filter unit;

FIG. 2 is a section through the filler head, along the line II-II in FIG. 3;

FIG. 3 is a section along the line IIIIII in FIG. 2;

FIG. 4 is an enlarged section along the line IV-IV in FIG. 2;

FIG. 5 is a section along the line VV in FIG. 1, to show the fixing mechanism;

FIG. 6 is a section along the line VIVI in FIG. 1, to show the top welding arrangements;

FIG. 7 is a section along the line VIIVII in FIG. 1, to show the cooler;

FIG. 8 is a section along the line VIIIVIII in FIG. 1, to show the bottom welding arrangements; and

FIG. 9 is a longitudinal section of the adjusting mechanism serving to bring the operating cycle of the filter element feed into line with that of the cutting mechanism.

In the equipment shown in way of example in FIG. 1, the arrangement for continuously feeding a succession of uniformly spaced and axially aligned filter wads, 1 and 2, on to a continuously fed filter-tip cover strip, 3, include a machine, 4, known in the cigarette industry as a Molins D.A.P.T.C. Machine, which is described in detail in U.S. Pat. No. 2,957,285. This machine 4 has two magazines, 5, for holding lengths of filter material, such as cellulose and acetate, for example, and two rotary drums, 6, which serve to receive them. The machine 4 is worked by the driving chain 7.

Round their periphery, the drums 6 contain grooves, running parallel to their axes of rotation, to receive the lengths of filter material, the drums also having radial cutouts in which cutters rotate for dividing the rod-like lengths of filter material into the smaller filter wads l and 2.

The rod-like lengths of filter material having been divided into the smaller filter wads l and 2, these are released by the drums 6 on to a spacing and conveying mechanisms, 8, by which the wads 1 and 2 are alternately fed forwards in axial alignement, in the direction of the arrow 9, and simultaneously spaced uniformly apart.

Next, the uniformly spaced and axially aligned filter wads l and 2 are fed continuously to a filter-tip cover strip, 3, likewise continuously fed, on which they are deposited, being guided at the sides, as shown in FIG. 5, by the guide members 10 and 11 and held in place, in relation to one another, by a pressure band, 12, situated above and running round in synchrony with the cover strip 3.

That face of the cover strip 3 which lies towards the filter wads l and 2 is coated with an adhesive such as, for instance, a thermoplastics, which softens under the action of heat, so that it is possible for the individual filter wads l and 2, directly they have been discharged on to the cover strip 3, to be secured to it with the aid of a heater, 13, thereby preventing relative motion, that is to say preventing any alteration in their spacing. As can be seen from FIG. 5, the cover strip 3 rests on a support, 14, while the heater 13 can be pressed from below, through a slot in the support 14, against the cover strip 3 and thus indirectly against the filter wads 1 and 2 that require to be anchored in place. The temperature of the heater 13 should preferably be thermostatically controlled. The heater 13 is so arranged that it can be moved clear of the cover strip 3 when this is stationary, to avoid burning it.

The individual filter wads 1 and 2 having been secured to the cover strip 3, the latter is fed on to an endless conveyor belt, 15, these parts being fed jointly on to a guide track that functions as a shaper, on which the cover strip 3, as it moves forward, is wrapped round the filter wads 1 and 2 attached to it, so as to form at least approximately a letter U. This assembly is then carried by the conveyor belt 15 to a filler head, 16, shown in greater detail in FIGS. 2, 3 and 4, which serves for the introduction of free-running filter material such as charcoal, for example, into the space 17 formed between the individual filter wads l and 2. To ensure proper filling of the spaces 17 with the filter material, the downward-facing discharge side of the storage container 18 of the filler head 16 is connected to a suction arrangement, 21, situated (when considered in relation to the directon of motion of the cover strip 3) before the charge aperture 20 of the filler head 16, by a sliding member, 19, which rests on the filter wads l and 2 and encloses them to the extent of at least The width of the sliding member 19 is approximately equal to the diameter of the filter wads 1 and 2 it is desired to wrap in the cover strip 3, the side faces 19a and 19b running parallel to each other and to the direction of motion of the conveyor belt 15 and serving to provide sealing contact with the inner faces 3a and 3b of the U-arms of the cover strip 3. In this way, spaces bounded by the end faces of the filter wads l and 2, the cover strip 3 and the sliding surface of the sliding member 19 are formed at 17.

The distance between the suction aperture 22 and the charge aperture 20 is greater than the length a of the spaces 17 formed between the wads 1 and 2, so that, as the wads advance, these spaces, between the suction aperture 22 and the charge aperture 20, are to all intents and purposes enclosed so as to be completely airtight, apart from the filter wads l and 2, the result being that the suction arrangement 21 is able to evacuate these spaces through the wads 1 and 2. Because of the partial vacuum prevailing in the spaces 17, the U- arms of the shaped cover strip 3 are held and virtually sealed against the side faces 19a and 19b of the sliding member 19.

The length of the suction aperture 22 in the sliding face of the sliding member, measured in the direction of travel of the cover strip 3, is greater than the maximum length b of the wads to be covered, so that the suction is able to act also on the end faces of the wads between which the spaces 17 to be evacuated are situated. This is particularly important where the filter wads in use have their lowest flow resistance in the axial direction. Moreover, the entire filter wad adjacent to the space 17 to be evacuated is thus brought under partial vacuum, so that nothing can detract from the effectiveness thereof.

The spaces thus evacuated arrive forthwith under the discharge aperture 20 of the storage container 18, which constitutes the charging aperture, whereupon the free-running filter material in the container is sucked instantaneously into the spaces 17 extending from the sliding face.

' In order to promote complete filling of the spaces 17 and the follow-up flow of the filter material in the container 18 down through the discharge slit 20, the filler head 16 is equipped with a vibrator, 23, the effect of which is to cause the filler head 16, mounted resiliently on flat springs (24, in FIG. 3), to vibrate at 100 cycles per second in a vertical plane.

The filler head 16 is suspended by the springs 24 from a guide, 26, which runs parallel to the track 25 provided for the conveyor belt 15, and clamped to the said guide by means of screws, 27. The screws 28 serve for horizontal alignment of the sliding member 19 in relation to the filter wads l and 2 below it, while the screws 29, rigidly connected to the guide 26, enable the amplitude of vibration of the filler head 16, imparted by the vibrator 23, to be regulated.

Since the width of the sliding member 19 is approximately equal to the diameter of the filter wads, the discharge slot can be made relatively broad, this being very important for unhindered follow-on of the freerunning filter material. At the end of the discharge slot 20 is a semi-circular trimming edge, 30, which bounds the cross-section of the filter wads l and 2 as they pass through and trims off the excess of free-running filter material. This trimming edge 30, being exposed to heavy wear when the equipment is running, is provided on an interchangeable trimmer, 31, which .can be inserted into the sliding member 19.

The underside of the trimmer 31 is provided with transverse grooves, 310, which remove any grains of the free-running filter material that still remain on the filter wads, pick them up and release them into the succeeding spaces 17.

Because, when certain free-running filter materials are used for filling, an undesirable amount of dust arises, which is deposited on the upper face of the filter wads and darkness them, the trimmer.3l may also be equipped with a suction aperture, through which the dust coating can beremoved by the creation of a very slight partial vacuum.

To enable the size of the discharge slot 20 to be adapted to the particle size of the free-running filter material, the bottom portion, 32, of the storage container 18 is made cylindrical. Within this bottom portion is a scoop-like closing member, 33, in sliding contact with the interior face of the cylindrical member 32 and designed to turn about the longitudinal centre line thereof. For rotating the closing member 33, there is a handle, 34, while a stud, 36, thrust by a spring towards the semi-circular plate 35, can drop home into recesses in various positions on the plate 35. The closing member 33 is thus shaped like a section of the curved'surface of a cylinder and is made as thin as possible, so as to keep to the minimum the force that needs to be exertedon the handle 34 to move the closing member when the container 18 is full. The closing edge of the closing member 33, moreover, is also'made oblique or sharpened in relation to the inner face of the cylindrical member 32, so as to'faeilitate movement of the closing member 33, and it runs helically round the longitudinal axis 37 of the cylindrical member 32, so that as the closing member 33 is turned in the direction for opening, it is initially the end of the discharge slot 20 that lies towards the suction aperture 22 which is freed, this being followed by those parts of the discharge slot 20 which are farther from the suction aperture 22 as the closing member continues to turn.

There is also advantage in thus being able to close the discharge slot 20 when the running of the installation is interrupted or when the clamping screws 27 are released and the filler head 16 is removed to expose the cover strip 3 that lies below and carries the filter wads l and 2.

To prevent the storage container 18, which is fed from the reverse container 38 (FIG. 1), from being over-filled, it is entered by two lengths of pipe, 39, each with its top end joined to a feed pipe, 40, for the freerunning filter material, and with its bottom end situated at the filling level of the container 18. In the example illustrated, the pipe 39 nearer to the suction aperture 22 contains a cutout, 41, facing towards the suction aperture, to increase the outflow of filter material, the consumption of which is greatest at that point. To cut off the supply of filter material from the reserve con-- tainer 38, the storage container 18 is also provided with a shutter, 42, which can be slid across the lower ends of the feed pipes 40.

In theterminal portion 43 of the sliding member 19, the upper part 44 of the track 25 is so shaped that the cover strip 3 is converted into a complete tube, a suction device being provided at 45 for the removal of any free-running filter material remaining between the edges of the cover strip.

For joining together the now overlapping edges of the cover strip, there now follows a sealing unit, 46, which, as shown in FIG. 6, has a heatable element, 47, which can be applied to the tube that is to be sealed. To prevent any of the free-running filter material, in filter tips fitted to cigarettes, from finding its way between the outside of the filter wads and the inside of the cover strip and into the smokers mouth, the cover strip should be stuck to the filter wads round their entire periphery.

To that end, the heatable element 47 is provided with a guidance channel, 48, semi-circular in section, its radius of curvature being the same as the outside radius of the tube that is to be produced. To achieve precision in the diameter of the tube produced, the guidance channel 48 in the heatable element 47 is immediately followed by another such channel 49, in a cooling unit, 50, which can be lowered on to the tube so as to cause the heat-softened plastics to set.

When the tube has been struck together, it is passed to a cutting head, 51, in which it is divided up in such a way that the length of each filter assembly is six times the length of a filter for a cigarette.

As the cutting head 51 must be precisely synchronised with the movement of the, filter wads within the finished tube, a timing mechanism, 52 (FIG. 9), is also provided, to synchronise the machine 4 feeding the tilter wads l and 2 on to the cover strip 3 with the drive of the cutting head 51 by which the tube filled with filter material is divided into given lengths.

The drives of the feed mechanism 4 and that of the cutting head 51 are linked together by a two-part shaft, 53a/53b. Between the first part 53a and the second part 53b of the connecting shaft is an adjusting member, 54,

which rotates with the latter, for altering the relative angular position of the two parts 53a and 53b of the shaft.

The adjusting member 54 has two parts, 55 and 56, in axial alignment, which can slide axially in relation to each other, the part 56 bearing guides, 57, which engage in helical grooves, 58, in the other part, 55.

To shift part 56 of the adjusting member in the axial direction in relation to the other part 55, a spindle, S9, driven by an electric motor, is provided, which in rotating displaces the intermediate member 60 and hence also the part 56.

Beyond the cutting head 51 is another adhesive joining unit, 61 (FIGS. 1 and 8), in which the heater 62 bears against the tube from underneath. The guide channel 63 in this heater is semi-circular in section and cements the as yet uncemented part of the cover strip 3 formed into a tube to the filter wads 1 and 2, so that these adhere to the cover strip 3 round their entire periphery and no free-running filter material can escape from the spaces 17, between the faces of the wads and the strip 3. Endless spiral wires, 64, run round and exert pressure on the upper side of the length of tube.

Experiments have shown that with such equipment, when a partial vacuum of at least 5 cm. of mercury column is applied, the amounts of a free-running filter material such as used hitherto that can be filled into the spaces 17 between the filter wads 1 and 2 are twice as great as when no vacuum is applied, with an output of about 4,200 filter units a minute. This clearly demonstrates the effectiveness of the suction arrangement 21.

Even with such a high output, the spaces in the filters are tightly filled, and the complete freeing of the upper sides of the wads from the free-running filter material and from filter material dust by the trimmer 31 and the suction device 45 produces clean cut surfaces when the filter units are divided by the cutting head 51.

What we claim is:

l. A method of manufacturing a cigarette filter in which sections of fibrous and sections of free-running filter materials are arranged in succession, which comprises the steps of securing succession of filter elements or wads, uniformly spaced and in axial alignement, to a continuously fed filter-tip cover strip there being provided between adjacent filter wads a succession of spaces, with feed apertures, for fillings of freerunning filter materials;

continuously advancing the resulting cover strip into and through a fixed zone of reduced pressure wherein air is evacuated from each successive space in closed-off state;

continuously moving the filter strip, with spaces in closed-off state, to and in contact with a filler head having at least one filling aperture where each said space in succession is opened to said filling aperture;

discharging through each said feed aperture into each said open space in succession a predetermined quantity of free-running filter material from said filling head;

then bringing together the edges of the cover strip in overlapping relationship so as to form a tube completely enclosing the filter wads and intervening fillings of free-running filter material in said spaces; and

firmly cementing together the overlapping edges of the strip to complete the so-formed tube.

2. A device for manufacturing cigarette filters in which sections of fibrous and sections of free-running filter materials are arranged in succession, which comprises;

a feed mechanism for continuously advancing a cover strip in one direction;

means for continuously feeding a succession of uniformly spaced and axially aligned filter wads on to the continuously advanced cover strip;

means fixing the individual filter wads to the cover strip; means of guidance and conveyance by which the cover strip bearing the spaced apart filter wads is guided and continuously fed forward;

a forming member adjacent said means of guidance and conveyance by which the cover strip, as it moves forward, is wrapped round the spaced apart filter wads attached to it so as to form at least approximately a letter U;

a stationary suction arrangement fitted above the means of guidance and conveyance, such that it makes contact, between the arms of the U-shaped cover strip, with the upper sides of the filter wads travelling forward with the cover strip and the facing inner surfaces of the U-shaped cover strip; whereby air is evacuated through said filter wads and through said intervening spaces;

means substantially sealing the spaces so evacuated;

a filling head for charging free-running filter material into the evacuated spaces between the wads, this filling head being situated above the means of guidance and conveyance and connected to the suction arrangement by a common sliding surface which makes a sealing contact on the upper sides of the filter wads travelling forward with the cover strip;

a guide member shaping the cover strip into a tube completely enclosing the filter wads and the spaces between them filled with free-running filter material, so that the edges of the cover strip overlap;

means for joining together the overlapping edges of the cover strip; and

means whereby the tube filled with sections made up of filter wads and filling of free-running filter material is divided up into given lengths.

3. A method as claimed in claim 1, characterised by the fact that a cover strip is used which has that side which comes into contact with the filter wads coated with a thermoplastic, and that the filter wads are joined to the cover strip by the application of heat, at least at particular points, to soften the thermoplastic coating.

4. A method as claimed in subsidiary claim 1, in which the cover strip, after the formation of a tube completely enclosing the filter wads and the freerunning filter material, is joined to the wads round their entire periphery by the application of heat for softening the thermoplastic coating.

5. A method as claimed in claim 1, in which use is made of a filler head in which the filling aperture can be regulated.

6. A method as claimed in claim 1, in which a partial vacuum of at least 3 cm., and preferably at least 5 cm., of mercury column is created in the evacuation zone in contact with the filter wads.

7. A method as claimed in claim 1, in which the filler head which has the filling aperture is caused to vibrate in the direction of filling.

8. A method as claimed in claim 1, in which the filler head is caused to vibrate at a frequency of cycles per second in the direction of filling.

9. A device as claimed in claim 2, in which the means of fixing the individual filter wads (1 and 2) to the cover strip (3) consists of a heater (13), which is movable towards and away from that side of the cover strip which faces away from the filter wads, and in which a shift mechanism is provided for bringing the heater (13) close enough to the cover strip (3), as this moves forward, for the adhesive on the cover strip, which softens under heat, to be softened at least at given points, the said mechanism moving the heater far enough away from the cover strip (3) when this is at rest to prevent said cover strip from being damaged by the radiant heat from the heater (13). v

10. A device as claimed in claim 2, in which the means of guidance and conveyance consists of an endless conveyor belt (15).

11. A device as claimed in subsidiary claim 10 in which the forming member by which the cover strip (3), as it moves forward, is wrapped round the filter wads attached to it so as to form at least approximately a letter U, consists of a sliding plate (25) and a pressure device (12) hearing on the filter wads (1 and 2), which gradually shape the conveyor belt (15), along with the cover strip (3) moving with it, to the desired shape.

12. A device as claimed in claim 2, provided with means of synchronisation, for synchronising the drive of the feed (4), by which the filter wads (1 and 2) are fed on to the cover strip (3), with the drive for the means (51) by which the tube filled with filter material is divided into given lengths, the drives for the feed (4) and for the said dividing means (51) being linked together by a two-part shaft (53a/53b), and adjusting member (54) being provided between the first and second parts (53a and 53b respectively) of the connecting shaft and rotating with the second part (53b) for altering the angular position of the two parts (53a and 53b) of the connecting shaft, within given limits, in relation to each other.

13. A device as claimed in subsidiary claim 12, in which the adjusting member (54) has two parts (55 and 56) in axial alignment, which can slide axially in relation to each other, one of them bearing guides (57), which engage in helical grooves (58) in the other part (55); and in which means of adjustment (59) are provided for altering the axial position of at least one part (56) of the adjusting member (54) in relation to the other part (55) thereof.

14. A device as claimed in claim 2, in which the suction arrangement (21) and the filter head (16) are connected by a common elongated sliding member (19) extending in the direction of travel of the filter wads and providing a sliding face which forms a sealing contact on the upper sides of the wads (l and 2) travelling forward with the cover strip (3), the width of the sliding member is approximately equal to the diameter of the wads (l and 2) to be wrapped in the cover strip (3), and the side faces (19a and 19b) of the sliding member (19) are parallel to each other and to the direction of travel of the cover strip (3) and are such as to make a sealing contact with the facing surfaces (30 and 3b) of the arms of the U-shaped cover strip.

15. A device as claimed in claim 2, in which the distance between the suction aperture (22) in the sliding face and the charge aperture (20) is greater than the length (a) of the spaces (17) formed between the filter wads (l and 2).

.16. A device as claimed in claim 2, in which the.

length of the suction aperture (22) in the sliding face, measured in the direction of travel of the cover strip (3), is greater than the maximum length (b) of the filter wads (l and 2) to be covered.

means of heat.

17. A device as claimed in claim 2, in which the filter head (16) is equipped with a storage container (18), the discharge slot in which constitutes the charge aperture, and a means of closure (33) working in conjunction with the discharge slot is provided for the purpose of regulating the opening of the latter.

18. A device as claimed in claim 17, in which the bottom portion (32) of the storage container (18) is cylindrical, the means of closure being a scoop-shaped closing member (33), in contact with the interior face of the said cylindrical portion (32), about the longitudinal centre line of which it can be turned; and in which the closing edge of the closing member (33) runs helically round the longitudinal axis (37) of the cylindrical portion (32) of the storage container, so that as the closing member (33) is turned in the direction for opening, it is initially the end of the discharge slot (20) lying towards the suction aperture (22) which is freed, this being followed by those parts of the discharge slot which are farther from the suction aperture as the closing member continues to turn.

19. A device as claimed in claim 17, in which the storage container (18) is entered by at least one length of pipe (39), one end of which can be connected to a feed inlet for the free-running filter material, while the other end is situated at the filling level of the storage container.

20. A device as claimed in claim 2, in which the guide arrangement (43/44) for converting the cover strip (3) into a complete tube is provided with a suction device (45) for the removal of any free-running filter material remaining between the edges of the cover strip.

21. A device as claimed in claim 9, in which the means by which the overlapping edges of the cover strip incorporate a heatable element (47), which can be lowered on to the tube that requires closing; and in which the heatable element (47) contains a guidance channel (48), approximately semi-circular in section, the radius of curvature of which is equal to the outside radius of the tube to be produced; and in which the guidance channel (48) in the heatable element (47) is immediately followed by another such channel (49), in a cooling unit (50) provided for causing the heatsoftened adhesive to set.

22. A device as claimed in claim 21, in which the first heatable element is followed, in the direction of travel of the means of guidance and conveyance, by a second heatable element, the guidance channel in which (62) joins the as yet non-adhering part of the cover strip (3) formed into a tube to the filter wads.

23. A method as defined in claim 1, wherein the cover strip provided with spaced filter elements is maintained under reduced pressure until the same has passed beyond said filler head.

24. A method as defined in claim 1, according to which there is used a cover strip which is coated with a thermoplastic synthetic material at the side coming in contact with the filter elements, and the individual filter elements, before reaching the suction part, are fixedly connected with the covering strip by softening, at least in spots, the thermoplastic synthetic coating by means of heat; that thereupon the spaces, located between the individual filter elements, are evacuated and then filled with the free-flowing filter material, and that finally after formation of a closed tube, completely surrounding the filter elements and the fillings of freeflowing filter material, the covering strip is glued to the filter elements throughout their entire circumference by softening the thermoplastic synthetic coating by UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT NO. 3,762,281 DATED October 2, 1973 INVENTORtSt Charles Burrus and Serge Boegli It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

[73] Assignee: F. J. Burrus 8c Cie.

Signed and Sealed-this eleventh Of November 1975 [SEAL] Arresr:

RUTH C. MASON Arresting ()jfizer I UNITED STATES PATENT OFFICE v CERTIFICATE OF CORRECTION Patent No. 62,281 Dated October 2,v 1973 Inv nt fls) Charles Burrus and Serge Boegli It is certified that error appears 1T1 the above-identified patent and that said Letters Patent are hereby corrected as shown'below:

[73] Assignee F. Burrus 8c Cie;

Signed and sealed this 17th day of September 1974.

(SEAL) Attest: I

MCCOY M. GIBSON JR. 7 c.. MARSHALL ANN) Attesting Officer Commissienerof Patents F ORM PC4050 (10 69) 

1. A method of manufacturing a cigarette filter in which sections of fibrous and sections of free-running filter materials are arranged in succession, which comprises the steps of securing succession of filter elements or wads, uniformly spaced and in axial alignement, to a continuously fed filter-tip cover strip there being provided between adjacent filter wads a succession of spaces, with feed apertures, for fillings of free-running filter materials; continuously advancing the resulting cover strip into and through a fixed zone of reduced pressure wherein air is evacuated from each successive space in closed-off state; continuously moving the filter strip, with spaces in closed-off state, to and in contact with a filler head having at least one filling aperture where each said space in succession is opened to said filling aperture; discharging through each said feed aperture into each said open space in succession a pre-determined quantity of free-running filter material from said filling head; then bringing together the edges of the cover strip in overlapping relationship so as to form a tube completely enclosing the filter wads and intervening fillings of freerunning filter material in said spaces; and firmly cementing together the overlapping edges of the strip to complete the so-formed tube.
 2. A device for manufacturing cigarette filters in which sections of fibrous and sections of free-running filter materials are arranged in succession, which comprises; a feed mechanism for continuously advancing a cover strip in one direction; means for continuously feeding a succession of uniformly spaced and axially aligned filter wads on to the continuously advanced cover strip; means fixing the individual filter wads to the cover strip; means of guidance and conveyance by which the cover strip bearing the spaced apart filter wads is guided and continuously fed forward; a forming member adjacent said means of guidance and conveyance by which the cover strip, as it moves forward, is wrapped round the spaced apart filter wads attached to it so as to form at least approximately a letter U; a stationary suction arrangement fitted above the means of guidance and conveyance, such that it makes contact, between the arms of the U-shaped cover strip, with the upper sides of the filter wads travelling forward with the cover strip and the facing inner surfaces of the U-shaped cover strip; whereby air is evacuated through said filter wads and through said intervening spaces; means substantially sealing the spaces so evacuated; a filling head for charging free-running filter material into the evacuated spaces between the wads, this filling head being situated above the means of guidance and conveyance and connected to the suction arrangement by a common sliding surface which makes a sealing contact on the upper sides of the filter wads travelling forward with the cover strip; a guide member shaping the cover strip into a tube completely enclosing the filter wads and the spaces between them filled with free-running filter material, so that the edges of the cover strip overlap; means for joining together the overlapping edges of the cover strip; and means whereby the tube filled with sections made up of filter wads and filling of free-running filter material is divided up into given lengths.
 3. A method as claimed in claim 1, characterised by the fact that a cover strip is used which has that side which comes into contact with the filter wads coated with a thermoplastic, and that the filter wads are joined to the cover strip by the application of heat, at least at particular points, to soften the thermoplastic coating.
 4. A method as claimed in subsidiary claim 1, in which the cover strip, after the formation of a tube completely enclosing the filter wads and the free-running filter material, is joined to the wads round their entire periphery by the application of heat for softening the thermoplastic coating.
 5. A method as claimed in claim 1, in which use is made of a filler head in which the filling aperture can be regulated.
 6. A method as claimed in claim 1, in which a partial vacuum of at least 3 cm., and preferably at least 5 cm., of mercury column is created in the evacuation zone in contact with the filter wads.
 7. A method as claimed in claim 1, in which the filler head which has the filling aperture is caused to vibrate in the direction of filling.
 8. A method as claimed in claim 1, in which the filler head is caused to vibrate at a frequency of 100 cycles per second in the direction of filling.
 9. A device as claimed in claim 2, in which the means of fixing the individual filter wads (1 and 2) to the cover strip (3) consists of a heater (13), which is movable towards and away from that side of the cover strip which faces away from the filter wads, and in which a shift mechanism is provided for bringing the heater (13) close enough to the cover strip (3), as this moves forward, for the adhesive on the cover strip, which softens under heat, to be softened at least at given points, the said mechanism moving the heater far enough away from the cover strip (3) when this is at rest to prevent said cover strip from being damaged by the radiant heat from the heater (13).
 10. A device as claimed in claim 2, in which the means of guidance and conveyance consists of an endless conveyor belt (15).
 11. A device as claimed in subsidiary claim 10 in which the forming member by which the cover strip (3), as it moves forward, is wrapped round the filter wads attached to it so as to form at least approximately a letter U, consists of a sliding plate (25) and a pressure device (12) bearing on the filter wads (1 and 2), which gradually shape the conveyor belt (15), along with the cover strip (3) moving with it, to the desired shape.
 12. A device as claimed in claim 2, provided with means of synchronisation, for synchronising the drive of the feed (4), by which the filter wads (1 and 2) are fed on to the cover strip (3), with the drive for the means (51) by which the tube filled with filter material is divided into given lengths, the drives for the feed (4) and for the said dividing means (51) being linked together by a two-part shaft (53a/53b), and adjusting member (54) being provided between the first and second parts (53a and 53b respectively) of the connecting shaft and rotating with the second part (53b) for altering the angular position of the two parts (53a and 53b) of the connecting shaft, within given limits, in relation to each other.
 13. A device as claimed in subsidiary claim 12, in which the adjusting member (54) has two parts (55 and 56) in axial alignment, which can slide axially in relation to each other, one of them bearing guides (57), which engage in helical grooves (58) in the other part (55); and in which means of adjustment (59) are provided for altering the axial position of at least one part (56) of the adjusting member (54) in relation to the other part (55) thereof.
 14. A device as claimed in claim 2, in which the suction arrangement (21) and the filter head (16) are connected by a common elongated sliding member (19) extending in the direction of travel of the filter wads and providing a sliding face which forms a sealing contact on the upper sides of the wads (1 and 2) travelling forward with the cover strip (3), the width of the sliding member is approximately equal to the diameter of the wads (1 and 2) to be wrapped in the cover strip (3), and the side faces (19a and 19b) of the sliding member (19) are parallel to each other and to the direction of travel of the cover strip (3) and are such as to make a sealing contact with the facing surfaces (3a and 3b) of the arms of the U-shaped cover strip.
 15. A device as claimed in claim 2, in which the distance between the suction aperture (22) in the sliding face and the charge aperture (20) is greater than the length (a) of the spaces (17) formed between the filter wads (1 and 2).
 16. A device as claimed in claim 2, in which the length of the suction aperture (22) in the sliding face, measured in the direction of travel of the cover strip (3), is greater than the maximum length (b) of the filter wads (1 and 2) to be covered.
 17. A device as claimed in claim 2, in which the filter head (16) iS equipped with a storage container (18), the discharge slot in which constitutes the charge aperture, and a means of closure (33) working in conjunction with the discharge slot is provided for the purpose of regulating the opening of the latter.
 18. A device as claimed in claim 17, in which the bottom portion (32) of the storage container (18) is cylindrical, the means of closure being a scoop-shaped closing member (33), in contact with the interior face of the said cylindrical portion (32), about the longitudinal centre line of which it can be turned; and in which the closing edge of the closing member (33) runs helically round the longitudinal axis (37) of the cylindrical portion (32) of the storage container, so that as the closing member (33) is turned in the direction for opening, it is initially the end of the discharge slot (20) lying towards the suction aperture (22) which is freed, this being followed by those parts of the discharge slot which are farther from the suction aperture as the closing member continues to turn.
 19. A device as claimed in claim 17, in which the storage container (18) is entered by at least one length of pipe (39), one end of which can be connected to a feed inlet for the free-running filter material, while the other end is situated at the filling level of the storage container.
 20. A device as claimed in claim 2, in which the guide arrangement (43/44) for converting the cover strip (3) into a complete tube is provided with a suction device (45) for the removal of any free-running filter material remaining between the edges of the cover strip.
 21. A device as claimed in claim 9, in which the means by which the overlapping edges of the cover strip incorporate a heatable element (47), which can be lowered on to the tube that requires closing; and in which the heatable element (47) contains a guidance channel (48), approximately semi-circular in section, the radius of curvature of which is equal to the outside radius of the tube to be produced; and in which the guidance channel (48) in the heatable element (47) is immediately followed by another such channel (49), in a cooling unit (50) provided for causing the heat-softened adhesive to set.
 22. A device as claimed in claim 21, in which the first heatable element is followed, in the direction of travel of the means of guidance and conveyance, by a second heatable element, the guidance channel in which (62) joins the as yet non-adhering part of the cover strip (3) formed into a tube to the filter wads.
 23. A method as defined in claim 1, wherein the cover strip provided with spaced filter elements is maintained under reduced pressure until the same has passed beyond said filler head.
 24. A method as defined in claim 1, according to which there is used a cover strip which is coated with a thermoplastic synthetic material at the side coming in contact with the filter elements, and the individual filter elements, before reaching the suction part, are fixedly connected with the covering strip by softening, at least in spots, the thermoplastic synthetic coating by means of heat; that thereupon the spaces, located between the individual filter elements, are evacuated and then filled with the free-flowing filter material, and that finally after formation of a closed tube, completely surrounding the filter elements and the fillings of free-flowing filter material, the covering strip is glued to the filter elements throughout their entire circumference by softening the thermoplastic synthetic coating by means of heat. 